Contiguous NPN or PNP regions and bipolar transistors are much used in modern electronics as individual devices and as part of various integrated circuits (ICs). The stability of such devices as a function of time and/or usage is an important property. It has been found under some circumstances, that the base current, the collector current, the current gain and/or other properties of such devices may drift as a function of time and/or usage. This is undesirable. Accordingly, a need continues to exist for improved bipolar transistors and other contiguous NPN or PNP regions, and methods for manufacturing the same, in which such drift in properties is reduced or eliminated.